Method of preparing phosphoric acid esters of aliphatic alcohols



Patented July 16, 1935 i t i 2,008,478

METHOD OF PREPARING PHOSPHORIC ACID ESTERS, 0F ALIPHATIC ALCOHOLS Byron M. Vanderbilt and Hans B. Gottlleb, Chicago Heights, 111., assignors to Victor Chemical Works, a corporation of Illinois No Drawing. Application June 13, 1934,

Serial N0. 730,520

t 11 Claims. (01. zoo-99am This invention relates to an improved method chloride is removed irom the mixture by the adof preparing phosphoric acid esters of aliphatic dition of an alkali and suflicient water to initiate alcohols. the reaction between the alkali and the hydrogen It has been heretofore suggested that neutral chloride. The hydrogen chloride is'thus neuphosphoric acid esters of certain primary alcotralized, forming water and an alkali chloride, 5 hols, such as butyl alcohol, might be. prepared the latter iormlngavoluminous precipitate which by the interaction of phosphorus oxychloride and may be filtered oil. The filtrate, containing the the alcohol at low temperatures to form the di- Ph p r te y excess of 81901101, and a substitution product, followed by heating at rela- Slight mo t of Wa e Saturated With alkali tively elevated temperatures to form the tri-sub- C o de, y ow e heated, first removing the 10 stitution product. In carrying out such amethod lcohol-Wa r f ac ion, an fi l y h tria1ky1 the hydrogen chloride gas formed s a by-prodester, without danger of side reactions due to the not in the initial reaction reacts to a considerhydrogen o de.

able extent with the alcohol, and at the same In COunectiOn with 810011015 forming a D time there are other side reactions which occur mixtures W Wate the a c o ay be reeov- 15 at the advanced temperatures which are used for e in anhydrous o y a on. the substitution of the third alkoxy group. In Th f llowing ar e amp s f t inv ntion: order to drive the reaction to completion it has 1800 Erams 0f butunol (normal butyl a100- been suggested that a very large excess or the 1!101) were Placed in 8 3 liter three-necked fi alcohol be used, but this does not greatly affect quipp d w a st rr thermometer a d s para- 20 the side reactions. It has been further suggested 'y funnel- The flask Was o d Externally t to remove part 01' the hydrogen chloride during p ae below d 460 grams f the reaction by the use or heat and vacuum, but phorus oxy hloride (B. P- 105107 0-) added this is impractical because of the corrosive na- W Y r B Period 01 one hourh k n 26 ture of the hydrogen chloride and because of its contents were maintained at a temperature the dimculty in removing more than a minor t e an a p d f Ove 48 proportion of such hydrogen hl rid hours to complete the reaction. The mixture was While it has heretofore been believed necessary then externally cooled to about Zero degrees a d to use an elevated temperature for the substi- 400 grams of we added- Suflicient heat was 30 tution of the third alkoxy group, it has now been evolved as the hydrogen chloride Partially (116- 30 discovered that the substitution may b solved in the ice water, to completely melt the plated at temperatures below 20 C. providing ice and 111188 the tempeature to about C- a long digestion period is used. It has further Then grams of soda as we slow y added been discovered that by proceeding at such low under od a itat on to p eve foaming se temperatures, and digesting until the r t After the addition of the soda ash was complete 35 is complete, the deleterious effect of the hydrothe mixture wa 1101011881 Cooled, but w t ed chloric acid gas may be avoided, and an increased vigorously tor 15 minutes to get the last traces of yield of the phosphoric acid esters obtained in the d ash o ea e sodium chloride prepure state. At the same time better than 99% c ni ate w quite voluminous and absorbed most 40 or the excess alcohol may be recovered. or th water, the mixture s pa at n nto two 40 It has been further discovered that during the aye The il lay r which was par a sa uformation of the trialkyl phosphates 3113 l t rated with aqueous sodium chloride solution was peratures it is unnecessary to remove the hydecantedirom the precipitate. The precipitate drogen chloride, and that after the reaction is wi h dhe n liq Poured Onto a filter and complete the hydrogen chloride may be removed Sucked 88 88 possible- The Water ye in 45 from the reaction product without the necessity the filtrate was then separated by means of a of utilizing heat, thus avoiding Substantially all separatory funnel, and the combined amounts side reactions due to hydrogen chloride. 01 oil from this separation and the decantation In carrying out the invention, phosphorus oxywere placed in a distillation flask. This oily chloride and a primary aliphatic alcohol are liquid consisting of the tributyl phosphate, ex- 50 mixed, thetemperature being maintained below cess butanol, aqueous salt (NaCl) solution dis- 20 C., and the mixture is maintained for it solved in the mass, and any traces of mono and period of 24-72 hours at or below this temdibutyl phosphates which might have been perature. formed were subjected to fractional distillation After the reaction is complete the hydrogen under a vacuum or about mm. Hg pressure, 55

the water-butanol fraction distilling oif flrst followed by anhydrous butanol and finally the tributyl phosphate is distilled over at a temperature or 147 C. after increasing the vacuum to about 9 mm. of Hg pressure. The residue in the still contains the sodium chloride impurity and the traces of any mono or dibutyl phosphates which might have been formed.

In accordance with this procedure tributyl phosphate yields of 88 to 95% may be easily at tained with better than a 99% recovery of the excess butanol used.

2. 1440 grams of anhydrous normal propyl alcohol were maintained at a temperature below 10 C. and 460 grams of phosphorus oxychloride added under good agitation. The mixture was maintained at 10 C. for 18 hours and at 15 C. for 44 hours and a separation of the hydrogen chloride in the manner described in Example 1 was made and the product worked up by fractionation to yield 567 grams of tri-n-propyl phosphate (B; P. 119 C. at 9 mm. Hg pressure) or 85% on the basis of the oxychloride used. 98 to 99% of the excess propyl alcohol can be recovered by fractionation.

3. 448 grams iso-amyl alcohol were cooled to 10 C. and 102 grams of phosphorus oxychloride slowly added. The mixture was maintained at 10 C. for 2 hours'and 15 C. for 45 hours, and then treated in the manner described in Example l to remove the hydrogen chloride and separate the excess of alcohol from the product. An 86% yield of tri-isoamyl phosphate (B. P. 143 C. at 3 mm. Hg pressure) was obtained in this particular experiment.

It is preferred to use alcohols which form phosphoric acid esters that are insoluble in water in order to avoid hydrolysis of such esters. However, very good yields of tri-ethyl phosphate may be obtained by this method, without apparent substantial hydrolysis in spite of the solubility of the ester. It is also preferred to use primary alcohols, owing to the greater activity of the secondary and tertiary alcohols toward hydrogen chloride.

The foregoing detailed description has been given for cleamess of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

What we claim as new and desire to secure by Letters Patent, is:

1. A process for the production of neutral phosphoric esters of aliphatic alcohols which comprises mixing phosphorus oxychloride with a primary aliphatic alcohol, digesting the mixture until the reaction is substantially complete, whereby a phosphoric ester and hydrogen chloride are formed, neutralizing the hydrogen chloride with an alkaline alkali metal compound, the temperature being maintained below 20 C. durin: all of said steps, and separating the phosphoric ester from the reaction mixture.

2. The method as set forth in claim 1, in which the digestion-is continued for a period of at least 24 hours.

3. The method as set forth in claim 1, in wh ch the alcohols are primary aliphatic alcohols having at least two carbon atoms.

4. The method as set worth in claim 1, in which the alcohols have at least two carbon atoms, and

in which a small amount of water is added to initiate the reaction between the hydrogen chloride and the alkaline agent."

5. The method for the production of neutral phosphoric acid esters which comprises mixing phosphorus ozwchloride with a primary aliphatic alcohol containing two or more carbon atoms, digesting the mixture until the reaction to form the phosphoric ester is substantially complete, adding a small amount of water and an alkaline alkali metal compound to neutralize the hydrogen chloride resulting from the esteriiication, the temperature being maintained below 20 C. durin: said steps, and separating the resulting alkali metal chloride from the reaction product.

6. The method as set forth in claim 5, in which thealkaline agentissodaash.

'l. The method as set forth in claim 5, in which excess alcohol is used and the excess is recovered by fractional distillation irom' the reaction mass after separation of the chloride.

8. The method as set forth in claim 1, in which the alcohol is a primary butyl alcohol and the product is tributyl phosphate.

9. The method as set forth in claim 1, in which the alcohol is a primary amyl alcohol and the product is triamyl phosphate.

10. The method as set forth in claim 1 in which the alcohol is primary propyl alcohol and the product is tripropyl phosphate.

11. The method as set forth in claim 5. in which the water does not exceed 20% by weight on the basis of the total reaction mass.

BYRON ll. VANDERBILT. HANS B. GUI'I'IIEB. 

